Automatic cut-off devices particularly for electric smoothing irons



April 23, 1957 R. J. MARRIOTT El AL AUTOMATIC CUT-OFF DEVICES PARTICULARLY FOR 1 ELECTRIC SMOQ'I'HING IRONS FilQd D60 14, 1954 III Foam. J/Vamvwrfi: 4/ NE (ant/E United States Pat-emf) AUTOMATIC CUT-OFF DEVICES PARTICULARLY FOR ELECTRIC SMOOTHING IRONS Ronald James Marriott, Toorak, and John Francis Coyne,

Malvern, Australia, assignors to Hecla Electrics Proprietary Limited, South Yarra, Victoria, Australia, a company of Victoria 'This invention relates to thermostat control devices for electrical smoothing irons and various other electrical appliances having a heating element and more particularly concerns that type of device which is manually adjustable over a predetermined temperature range and incorporates a bimetallic or other heat sensitive element for effecting the desired opening and closing movements of an associated switch.

Known thermostat control devices of the type mentioned, have proved to be satisfactory for existing types of smoothing irons, but are not sufficiently sensitive to meet the requirements, for example, of a novel type of pressing iron which forms the subject of our copending United States patent application and which functions to rapidly distribute steam, from the damp fabric, that is normally trapped beneath the iron.

The primary object of the present invention is to provide an improved device of the kind indicated, which is more sensitive than hitherto and capable of relatively fine temperature adjustment in accordance with requirements.

Another object is to provide an improved thermostat control device in the form of a unit which is preset to the desired temperature range at the factory and is capable of being quickly and easily fitted to and removed from an iron when required without having to change the setting.

Other objects and various novel constructional features of the invention will be more readily apparent from the following more detailed description which for convenience, relates to the application of the improved thermostat control device to an electric iron.

Referring to the drawings which form part of this specification:

Figure 1 is a longitudinal section showing the im proved thermostat control device fitted to an electriciron.

Figure 2 is a plan view of some of the parts seen in Figure l. l

Figure 3 is a cross section taken on the line III--III of Figure 1, parts being omitted for convenience of illustration.

Figure 4 is a fragmentary sectional plan view of some of the parts' seen in Figure 2.

Figure 5 is a longitudinal section on an enlarged scale, showing a bimetallic strip and associated wedge which form part of the improved device.

Electrical smoothing irons of the type to which this inventionis particularly applicable, include an iron sole 2 and 'a clamping plate 3 between which an electrical heating element 4 is held fast. The latter may consist of a ribbon like metal winding arranged in the form of a sandwich between sheets of mica or other insulating material.' A series of anchoring bolts 6 upstanding from the iron sole may be employed for connecting theassem shown) in the desired operative position.

It'accordance with the present invention, the int- "ice proved thermostat control device includes a heat conducting base plate 7 preferably in the form of a relatively thin metal stamping of substantially the same or part of the same shape and size as that of the clamping plate. This base plate, which carries an electrical switch and parts associated therewith, is adapted to be located between the iron sole and the heating element so as to constitute a relatively large heat conducting surface for influencing a thermostat element associated with the switch. The latter consists of fixed and movable contacts 8 and 9 preferably of silver to minimize pitting and which are carried by a fixed leaf and a resilient leaf 11 and 12 respectively.

'In order to avoid or minimize direct heating of these leaves they are spaced from and thermally insulated from the base plate for example, upon a plurality of upstanding posts 13 attached to the base plate. These posts may be located near the rear end of the base plate, and be connected to the fixed and movable leaves near the rear end of the latter so that the leaves may extend lengthwise of the base plate in overlying relationship.

The fixed leaf 11 is relatively stiff and for that purpose may be of substantially channel shape in cross section as seen more clearly in Figure 3. The movable leaf 12 is electrically insulated from the fixed leaf and is composed of spring like metal. The fixed and movable contacts are carried by their respective leaves near the front ends thereof whilst the rear ends of the leaves are adapted to be electrically connected in any suitable manner with contact pins or the like on the iron.

The aforesaid thermostat element preferably consists of a bimetallic strip 14 which may also extend lengthwise of the base plate beneath the forward end portion of the fixed and movable leaves. The bimetallic strip may be located in an air gap above an aperture 16 in the base plate with one end of the bimetallic strip thermally connected to a bridge 17 over the gap and which forms part of the base plate.

Associated with the foregoing are manually adjustable temperature control means including adjustable thrust transmission means for transmitting movement of the bimetallic strip 14 to the movable contact 9. Such thrust transmission means include a longitudinally ad justable wedge 18 which is loosely connected to the free end of the bimetallic strip. For this purpose, the latprovide a desirable line or usbstantially knife edge engagement between these parts.

Any suitable means are employed for effecting lengthwise movement of the wedge. For example, such means may consist of an upstanding oscillatable spindle 22 carried by the mounting means for the aforesaid leaves and which is connected to the rear end of the wedge by pivoted linkage 23. A limit stop 24 is preferably provided for restricting turning movement of the spindle which is also preferably spring influenced to oppose undesirable rotation.

The spindle 22 is fitted at its upper end with a pointer 26 associated with a fixed scale, for example, on the iron cover so as to indicate the temperature at which the iron is to operate. Tongue and groove connections are preferably employed for connecting the pointer to the spindle so that the pointer may be removed and replaced when required without disturbing the correct operative relationship between the pointer and its fixed scale.

Mounted upon the movable leaf 12 near the free end thereof, is a depending thrust pin 27 which is located in registry with'the top inclined face of the wedge. The effective length of this thrust pin is adjustable "and for this purpose the movable leaf may be fitted with a screwed bush which is electrically insulated from the leaf and adapted to carry the thrust pin. The latter 'is'sciiewc'd lengthwise and may-be provided at its upper endwith a slot for turning purposes-and also with a lock-nut 29. The fixed leaf 11 is provided with a hole "31 in substantial axial alignment with the thrust pin so thatthe latter may pass freely therethrough and be engaged by the wedge.

-It'will be appreciated-from the foregoing, that the'base plate, switch and manually adjustable thermostatcohtrol devices, may be formed'as a unitary assembly v'v'i'thfthe operative position of-the thrust pin preferably lp'resetat the factory. Such-a unit may-obviously-be 'readily 'fitted to and removed from an iron when required. I I

-In use, the effective area of the base plate 1 and its operative position 'in relation to the heating element 4 and the iron sole 2 enables 'it to rapidly-transfer heat from almost'the entire area of the iron sole "and also the heating element to the bimetallic strip 14. Up'on heating, the'fr'ee 'endof the latter warps upwardly and brings theupper edge of the wedge -18 carried-thereby into engagement with the lower end of the thrustfpin 27 for opening the contacts. Slight cooling-of 'the base plateenables the contactsto close and thils resumeheatng oftheiron sole for thepu'rpose of'maintainingit a't the, desired constant temperature. This temperature is easily determined by the user simply by turning "the pointer-26tothe required markin'gon the fixed scale. It will'be apparent from theforegoing, that the'tr'an'sfer of heat'by-conduction and radiation 'tothe biinetall-ic strip both from the. iron sole as well as -from the heating element is far more etlicient than hitherto, whilst the adjustable wedge andscrewed thrust pin renders'the device particularly sensitive.

Although the invention has been described with :par-

ticular reference to its application toan electricalsrnoothing iron, it will beunderstood that its use is not limited thereto as obviously the improved thermostat control device may be readily fitted, for example, to hot plates and a valiety of other electrical heating appliances.

Various other alterations, modifications and/or additions may be introducedintothe foregoing construction and arrangement of parts without departing from the ambit of the invention. as defined by the appended-claims. Having nowdescribed our invention, what we claim as new and desire tosccure by Letters Patent is:

'1. An improved thermostat control device of the kind indicated for use with electrical smoothing irons and other electrical appliances having a heating element, comprising an electrical switch mounted on said iron or other appliance andwired in circuit with said heating elemehha heat sensitiveelement fixedly mounted in 'relation tosaid switch in such a rnanner that part of said-heat sensitive element is movable in relation to the contacts of said switch and manually adjustable temperature control means located between said heat sensitive element and s'aid contacts whereby movement of said heat sen sitive element in response to temperature change's in -said smoothing iron or other appliance is adapted to effect relative movement between said contacts. I 2. An improve'dthe rmosta't control device of the kind indicated foruse with electricalsm'oothing irons and other electrical appliances having a heating element, comprising'a heat conducting base 'plate mounted between the heating element and part of the iron or other applian ce to be heated, an electrical switch wired in circuit with said heating element andwhich is fixedly mounted on said base plate and has relatively movable contacts one of whi'ch'is spring influenced so as normally to maintain said contacts closed, a heat sensitive element also fixedly mounted on said base plate in such amanner that partof said element is lmdvable towards and away from 1;

said spring influenced contact to open and close said contacts and manually adjustable 'temperature"'control means including adjustable thrust transmission means located between said spring influenced contact and the movable portion of said heat sensitive element so as to vary the degree of movement of said heat sensitive element that is required to open said contacts.

3. In an improved thermostat cerium device for use with electrical smoothing irons and other electrical appliances having apart to be heated and a'heating element for heating said part, the improvement comprising an electrical switch mounted on said appliance and wired in circuit with said heating element, a heat sensitive element fixedly mounte'd 'inr'elati'o'n 'to'said 's'witch in such a manner that part of said heat sensitive elernent is movable i'n relation to the contacts of said switch, and manually adjustable temperature control means located between said heat sensitive element and said contacts whereby movement of said sensitive element in response to temperature changes in said part "to be heated is adapted to "effect relative movement between saidco'ntacts, said manually adjustable temperature control means including'a longitudinally slidable wedge loosely mounted uponthe movable portion of'said heat sensitive element, a cooperating thrust member carried'by one 'of said "contacts and located in registry with the inclined face of said wedge, and means for moving said wedge lengthwise so as to vary the degree ofmovement of said-heat sensitive element that is required to open said contacts.

4. In an improved thermostat control device for use with "electrical smoothing irons and other electrical appliances having a part to be heated and a heating element for heating said part, the improvement comprising an electrical switch mounted on said appliance and wired in circuit with said heating element, a heat sensitive element fixedly mounted in relation to said switch in such a manner that part of said heat sensitive element is movable in relation to the contacts of said switch, and manuallyxadjustable temperature control means located between said heat sensitive element and said contacts whereby movement of said sensitive element in response to temperature changes in said part to be heated is adapted to effect relative movement between said contacts, said manually adjustable temperature control means including a longitudinally slidable wedge loosely mounted upon the movable portion of said heat sensitive element, aicooper'ating thrust member carried by one of saidc'o'ntac'ts and-located in registry with the inclined 'face of said wedge, and means for=moving said wedge'lengthwise "so as to-vary thedegree of movement of-s'aidheat sensitive element that is required to open said contacts, saidloose connection between the wedge and the heat sensitive element "consisting of laterally spaced and opposed'claws adapted to slidably engage longitudinal flanges on the opposite sides of said wedge, and a cross rib extending between said claws so as to be engaged by the bottom of the wedge and thus provide a line or substantially knife ed'ge engage'ment between these parts.

5. In an improved thermostat control device for use with electrical smoothing irons'and other electrical appliances having a part to be heated'and a heating element for heatingysaid part, the improvement comprising an electrical switch mounted on said appliance and wired in circuit with said heating element, a heat sensitive element fixedly mounted in relation to 'said switch in such a-rnanner that part of said heat sensitive 'element is movable in relation to the contacts of said switch, and -manually adjustable temperature control means located between said heat sensitive element and said contacts whereby movement of said sensitive element in response to temp'erature changes in said part to be heated is adapted to effect relative movement between said con= tacts, said manually adjustable temperature control means including a longitudinally slidable wedge loosely mounted upon the movable portion .of said heat sensitive element,

a cooperating thrust member carried by one of said contacts and located in registry with the inclined face of said wedge, and means for moving said wedge lengthwise so as to vary the degree of movement of said heat sensitive element that is required to open said contacts, in combination with an oscillatable spindle carried by said base plate and connected by pivoted linkage with said wedge, said spindle having an associated limit stop for restricting its movement and a pointer for providing a visible indication of such movement.

6. In an improved thermostat control device for use with electrical smoothing irons and other electrical appliances having a part to be heated and a heating element for heating said part, the improvement comprising an electrical switch mounted on said appliance and wired in circuit with said heating element, a heat sensitive element fixedly mounted in relation to said switch in such a manner that part of said heat sensitive element is mov able in relation to the contacts of said switch, and manually adjustable temperature control means located between said heat sensitive element and said contacts whereby movement of said sensitive element in response to temperature changes in said part to be heated is adapted to eifect relative movement between said contacts, said manually adjustable temperature control means including a longitudinally slidable wedge loosely mounted upon the movable portion of said heat sensitive element, a cooperating thrust member carried by one of said contacts and located in registry with the inclined face of said wedge, and means for moving said Wedge lengthwise so as to vary the degree of movement of said heat sensitive element that is required to open said contacts, which are arranged in overlying relationship above said heat sensitive element and the wedge carried thereby, said contacts being carried by leaves, one of which is fixed whilst the other is resilient so that its contact may be moved towards and away from its associated fixed contact, the spring influenced contact being provided with said thrust member the outer end of which is located adjacent to the inclined face of said wedge and means for adjusting the effective length of said thrust member.

7. An electrical smoothing iron or other appliance having a part to be heated, an electrical heating element and a thermostat control device wired in circuit with said heating element, said thermostat control device comprising a heat conducting base plate located between said heating element and said part to be heated, an electrical switch fixedly mounted on said base plate and having a pair of relatively movable contacts carried by overlying leaves, one of which is fixed whilst the other is resilient, a heat sensitive element in the form of a bi-metallic strip one end of which is thermally fixed to a bridge over an air gap in said base plate whilst the other end is free to flex towards and away from said movable contact, the resilient leaf of which carries a depending thrust pin which is screw threaded so that its efiective length may e varied, a longitudinally slidable wedge resting upon a cross rib on the free end portion of said bi-metallic strip and having a pair of laterally spaced and opposed claws adapted to loosely accommodate therebetween longitudinal flanges on the sides of said Wedge which is connected by pivoted linkage to an oscillatable spindle also carried by said base plate and provided with a limit stop and a pointer.

8. For use in an electric smoothing iron or other electrical appliance having a part to be heated, a thermostat control device in the form of a unit and comprising a heat conducting base plate having mounting means for an electric switch consisting of fixed and movable contacts carried by overlying leaves, one of which is fixed whilst the other is resilient, a heat sensitive element in the form of a bi-metallic strip thermally connected near one end to a bridge over an air gap in said base plate so that the free end portion of said strip is located between said leaves and the base plate, a longitudinally slidable Wedge loosely connected to the outer end portion of said himetallic strip so as to be located in registry with the free end of a longitudinally adjustable thrust pin carried by said resilient leaf and manually adjustable means for eifecting lengthwise movement of said wedge.

References Cited in the file of this patent UNITED STATES PATENTS 1,985,100 Kuhn et al Dec. 18, 1934 2,447,622 Ulanet Aug. 24, 1948 2,600,472 Brock June 17, 1952 2,602,873 Finlayson July 8, 1952 2,668,897 Beach et al. Feb. 9, 1954 

